1: Biochemistry. 2009 Feb 3;48(4):667-75.

Integration host factor (IHF) dictates the structure of polyamine-DNA
condensates: implications for the role of IHF in the compaction of bacterial
chromatin.

Sarkar T, Petrov AS, Vitko JR, Santai CT, Harvey SC, Mukerji I, Hud NV.

School of Chemistry and Biochemistry, Petit Institute of Bioengineering and
Bioscience, and School of Biology, Georgia Institute of Technology, Atlanta,
Georgia 30332, USA.

Integration host factor (IHF), a nucleoid-associated protein in bacterial cells, 
is implicated in a number of chromosomal functions including DNA compaction. IHF 
binds to all duplex DNA with micromolar affinity and at sequence-specific sites
with much higher affinity. IHF is known to induce sharp bends in the helical axis
of DNA in both modes of binding, but the role of IHF in controlling DNA
condensation within bacterial cells has remained undetermined. Here we
demonstrate that IHF influences the morphology of DNA condensed by polyamines in 
vitro. In the absence of IHF, spermidine and spermine condense DNA primarily into
toroidal structures, whereas in the presence of IHF, polyamines condense DNA
primarily into rodlike structures. Computer simulations of DNA condensation in
the absence and presence of IHF binding lend support to our model in which DNA
bending proteins, such as IHF and HU, promote the condensation of DNA into
rodlike structures by providing the free energy necessary to bend DNA at the ends
of linear bundles of condensed DNA. We propose that a common function of IHF and 
HU in bacterial cells is to facilitate DNA organization in the nucleoid by the
introduction of sharp bends in chromosomal DNA.


PMID: 19132923 [PubMed - indexed for MEDLINE]

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